Artisans in the field of rocket propelled missiles have for many years sought to combine the capability of the ordinary cannon, or artillery piece, operating by means of an explosive charge for launching projectiles and the like, with the steady state propulsion efficiency derived from the burning of a solid propellant in a rocket motor. These devices, known as rocket assisted projectiles, or gun boosted rockets, and with which this invention is concerned, have not, up to now, proved entirely satisfactory nor performed in accordance with expectations. Many reasons have been advanced for this, not the least of which is the failure to develop a propellant grain which can withstand the acceleration forces experienced during the difficult launching, or boost phase of the projectile flight, or to develop means to protect the grain. Success has heretofore been elusive most often in the past because of propellant grain cracking, or other similar deleterious effects induced by the high launching acceleration forces to which the propellant is subjected. It is, of course, quite obvious that the rocket motor propellant would be subjected to very high linear, tangential and radial acceleration forces during the launch of the missile and due to the spinning thereof imparted by the lands or rifling grooves on the inside surfaces of the barrel of the gun which fires the projectile. Accordingly, the invention to be hereinafter described provides, by means of a flowable propellant charge, hereinafter more specifically referred to as a fluidizable, shapeable propellant charge composition, and the advantageous use of the radial acceleration forces created by projecting the missile from a rifled gun barrel, a workable and operable rocket assisted projectile, which can be safely launched by means of ordinary field artillery equipment.